tongue drive system
TRANSCRIPT
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7TONGUE DRIVE SYSTEM
Presented by:
Anagha Balakrishnan
ER & DCI-IT,Vellayambalam
RollNo: 07
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What is TDS?
TONGUE–OPERATED assistive
technology for people with severe
disability to control their
environment
DEVELPOED by GT Bionics Lab
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Assistive Technology ?
ASSISTIVE TECHNOLOGY is an umbrella term
that includes assistive, adaptive, and
rehabilitative devices for people with
disabilities and also includes the process
used in selecting, locating, and using
them.
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Why Spinal Cord Injury is Fatal?
•SPINAL CORD is located
inside the spine
•CONNECTS the brain to
nerves in the body
•MESSAGE travel in very high
speed from brain to rest of
the body
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Cause of Spinal Cord Injury…
SPINAL CORD is squashed or blood
circulation of the spinal cord is cut off,
which will result in..
PARALYSIS
UNABLE to easy breath
UNABLE to feel pain or sensation
SORES on skin not being able to move around
SEXUAL dysfunction
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Existing Assistive Technologies…
Sip-and-Puff wheel chair
•USE air pressure to
control wheel chair by
sipping and puffing
•NOT good for people
with week breathing
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Voice activated powered wheelchair
•WHEN user speaks
commands, a
microphone in a throat
detects the vibration of
vocal cord
•UNSTABLE for powered
wheelchair control in
noisy
environments
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Head control
•WHEELCHAIR
controlled by head
control device
•NOT good for the
users with bad head
movement ability
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Why Tongue?...
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TONGUE and mouth occupies the major part
MUSCLE fibers in tongue is similar to heart muscle
fibers
LOW rate of Perceived Exertion
DIRECTLY connected to the brain
HIDDEN inside mouth will give a certain degree of
privacy
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TDS – Overview
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TDS –Overview…
SMALL permanent magnet pierced on the tongue
ARRAY of Hall-effect magnetic sensors senses the magnetic field
SENSORS mounted on a dental retainer and attached on the outside of the teeth
SMALL batteries are intended to power
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POWER management circuitry scans through the sensors and turn on one at a time
TDM analog output are digitized, modulated and transmitted to the external control unit through a wireless link
FROM their signals are demodulated, demultiplexed to extract individual sensor output
BY processing these output command is identified
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TDS Prototypes
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BUILD on a face shield
FUNCTION is to directly emulate mouse
pointing and selection function with the
tongue movement
SIX COMMANDS : up, down, right, left,
single click & double click
SSP algorithm running in background
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MAGNETIC TRACER : small, cylindrical,
rare-earth permanent magnet
PAIR of two-axis magnetic field sensor
modules- each contained a pair of
orthogonal magneto-inductive sensor
THREE AXIS MODULE: used as a reference
electronic compass to minimize the effect
of external magnetic field interference
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CONTROL unit & reference compass
hidden under face shield cap
ENTIRE system was powered by a 3.3V
coin-sized battery(CR2023)
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SENSOR output where send serially to the
ultralow-power MSP430 microcontroller
MICROCONTROLLER took 11 samples from
each sensor
SAMPLES are arranged in a data frame
and wirelessly transmitted to a PC across
a 2.4 GHz wireless link established
between nRF2401 transceivers
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Sensor Signal Processing algorithm DEVELOPED in MATLAB environments
2 phases: Training & Testing
•TRAINING : USES principal components
analysis
(PCA) to extract the most important
features of the sensor output waveforms
for each specific command
• USER repeats each of the
six designated commands 10 times in 3-
second intervals
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• TOTAL of 12 samples
(3 per sensor) are recorded in 12-
variable vectors
• THE PCA-based
feature-extraction algorithm calculates
the eigenvectors and Eigen values based
on the 12-variable vectors
• THREE eigenvectors
with the largest Eigen values are then
chosen to set up the feature matrix [v1,
v2, v3]
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• BY multiplying the
training vectors with the feature matrix,
the SSP algorithm forms a cluster (class)
of 10 data points from training for each
specific command
•TESTING: k-nearest neighbour (kNN)
classifier is then used in real time to
evaluate the proximity of the incoming
data points to the clusters formed earlier
in the training phase
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• kNN starts at the incoming new
data point and inflates an imaginary
sphere around that data point until it
contains a certain number (k) of the
nearest training data points
• IT associates the new data point
to the command that has the majority of
the training data points inside that
spherical region.
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AFTER finding the intended user
command, the mouse pointer starts
moving slowly in the selected direction
FOR faster access the user can
hold his or her tongue in the position of
the issued command and the pointer will
gradually accelerate until it reaches a
certain maximum velocity
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Training Session
GRAPHICAL user interface (GUI) prompted
the user to define each command by moving
his tongue from its resting position to the
corresponding command position when the
command light was on and returning it back
to the resting position when the light went
off
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THIS procedure was repeated 10 times for
the entire set of six commands plus the
tongue resting position, resulting in a
total of 70 training data points.
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Implementation
- Controlling a Powered Wheel Chair
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SYSTEM consists of the hall effect sensors
(A1231),
MSP430 microcontroller, H-Bridge driver
(SN754410)
Block diagram & hardware component
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4 ADC channels of MSP430 convert analog
signals from sensors to digital for
processing
BASED on the processed information
microcontroller drives the driver IC
DRIVER IC drives the DC powered
wheelchair
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SENSOR- Linear Bipolar Hall effect sensor
TRANSDUCER which varies its output
voltage in response to changes in magnetic field
•VOLTAGE:4.5V-5.5V
•OUTPUT is an analog
voltage that vary
from 0-5V
•THAT is converted to
a digital value by ADC
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H-BRIDGE DRIVER : used to drive the
wheelchair
SN7454410:BidirectionalH-Bridge driver
5V power supply is given
SPEED of the wheelchair is controlled by the
PWM signals from MSP430
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•4 SWITCHES
•WHEN A and D are closed,
a positive voltage applied
across the motor
•WHEN B and C are closed ,
voltage is reversed,
allowing reverse operation
of the motor
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DC Motors and Gear Box•5V DC motors with a gearbox
for driving the vehicle
•USED 2 motors: Left and right
•LEFT motor at rest and right
in motion turn vehicle left and
vice versa
•FOR forward and backward
motion both the motors are
driven in same direction with
same speed
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Software Components
ADC10(Analog to Digital converter)
•MSP430G2252 has 8 ADC channels of 10 bit each
•ADC10 convert the analog signal from the sensor
into digital value
•WE get the value ranging from 0-1023
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Pulse Width Modulation
•MODULATING technique which generates
variable width pulses is used to vary the
speed of the motor
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Algorithm
•ROUND ROBIN algorithm that implements
polling technique
•SENSOR values are always read one after
other in a continuous loop
•FEW threshold values set for each sensor
•IF reading from sensors reaches the threshold
value program triggers the change of state
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S1 & S2 front sensor , S3 & S4 back sensors
WHITE circle in the middle- resting position of
tongue
DIFFERENT flag values for each sensor
IF sensor is high, then the flag value remains high
until the operation is performed, then it is reset
again
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f1 - S1 > 750 // forward
f2 - S2 > 600 // backward
f3 - S3 > 700 // speed increase
f4 - S4 > 700 // speed decrease
f5 - S1 > 600 & S3 > 600 // turn left
f6 - S2 > 600 & S4 > 600 // turn right
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Advantages SIMPLE to implement , low cost, easy to
operate flexible
NO surgery needed
OFFERS better privacy to the user
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Drawbacks
USERS should avoid inserting
ferromagnetic objects in their mouth
MAGNETIC tracer should be removed
if the user is undergoing MRI
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CONCLUSI
ON
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QU
ES
TIO
N
TIM
E
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